Thixotropic Ink‐Engineered Flexible Sensors for Real‐Time Swelling Force Monitoring in LFP Batteries

Abstract The swelling behavior of lithium‐ion batteries provides critical insights into their operational status, offering significant potential for safety early‐warning systems. However, conventional flexible force sensors face substantial challenges in battery expansion monitoring due to stringent requirements regarding installation dimensions, measurement range, and long‐term durability. This study presents an innovative thin‐film force sensor based on fumed silica‐modified conductive ink, where the silica‐induced hydrogen bonding network effectively suppresses ink leveling during fabrication, thereby preserving controlled surface micro‐roughness in the printed functional layer. The optimized sensor demonstrates exceptional performance characteristics, including an extended pressure range (0–1200 kPa), rapid response time (<50 ms), and excellent cycling stability (>10 000 cycles). Integrated into a 4 × 4 sensing array, the system successfully monitors dynamic swelling force variations during the lithium iron phosphate (LFP) battery charge–discharge cycles. Furthermore, by combining voltage and swelling force data through an advanced data fusion algorithm, highly accurate state‐of‐charge estimation is achieved with 98.13% accuracy at 1% resolution, representing a significant improvement over conventional monitoring methods. This work establishes a new paradigm for battery safety management through mechanical signature analysis, providing both fundamental insights and practical solutions for next‐generation battery monitoring systems.